Minimally invasive neuro-surgical procedures require geometrically accurate, and patient-registered, imaging data to facilitate tissue differentiation and targeting. Thus far, true integration of imaging (pre-surgical and intra-operative), surgical access, and resection devices has not been accomplished. Medical devices remain separate systems, and the surgeon is required to cognitively integrate the information.
Pre-operative imaging data such as Magnetic Resonance Imaging (MRI), Computerized Tomography (CT) and Positron Emission Tomography (PET), is integrated into the surgical room statically through a viewing station, or dynamically through a navigation system. The navigation system registers devices to a patient, and a patient to the pre-operative scans, allowing for instruments to be viewed on a monitor in the context of the pre-operative information.
Intra-operative imaging systems primarily consist of microscopes, endo-scopes, or external video scopes. These are optical instruments that acquire, record and display optical wavelength imaging (2D, or stereoscopic) that is typically acquired at an increased resolution compared to what can be seen with the surgeon's unassisted eye. This optical information is typically displayed on a screen for the surgeon to view as a video feed, while the navigated MRI/CT/PET data would be presented on a separate screen.
Some attempts have been made to offer a small window on the navigation screen to show the optical video, or likewise showing overlays from the navigation screen on the optical video. Accurate registration between the modalities, effective interface between the surgeon and the devices, and true integration of the devices has remained elusive.
Port-based surgery is a minimally invasive surgical technique where a port is introduced to access the surgical region of interest using surgical tools. Unlike other minimally invasive techniques, such as laparoscopic techniques, the port diameter is larger than tool diameter. Hence, the tissue region of interest is visible through the port. Accordingly, exposed tissue in a region of interest at a depth few centimeters below the skin surface, and accessible through a narrow corridor in the port. Several problems generally preclude or impair the ability to perform port-based navigation in an intraoperative setting. For example, the position of the port axis relative to a typical tracking device (TD) is a free and uncontrolled parameter that prohibits the determination of access port orientation. Furthermore, the limited access available due to the required equipment for the procedure causes indirect access port tracking to be impractical and unfeasible. Also, the requirement for angulation of the access port to access many areas within the brain during a procedure makes navigation of the access port a difficult and challenging problem that has not yet been addressed.
Further, a recent paper by Stieglitz et al [Stieglitz, Lennart Henning, et al. “The silent loss of neuronavigation accuracy: a systematic retrospective analysis of factors influencing the mismatch of frameless stereotactic systems in cranial neurosurgery] Neurosurgery 72.5 (2013): 796-807.] highlights the need for accurate navigation, wherein after patient registration, there is an ongoing loss of neuronavigation accuracy due to other mitigating factors related to the surgical procedure (i.e., draping, attachment of skin retractors, and duration of surgery). Surgeons should be aware of this silent loss of accuracy when using navigation systems.
Thus, there is a need for a system and method to integrate and update pre-operative and intra-operative plans into navigation systems for minimally invasive surgical procedures.